In recent years, RAID has been used to improve reliability and fault tolerance in many storage apparatuses. In a storage apparatus using RAID, even if any of the storage drives configuring a RAID group is blocked due to a failure or the like, reading data or writing data can be continued by a fall-back operation using the remaining storage drives.
For such storage apparatuses, a technology has been developed which recovers the data stored in a blocked storage drive by using the data stored in a non-blocked storage drive in the same RAID group as the blocked storage drive during the fall-back operation, and writes the data to a storage drive prepared as a spare drive (hereinafter, also referred to as correction copy). Also another technology has been developed which writes the data recovered in the spare drive by the correction copy back to a new storage drive after the blocked storage drive is replaced with the new storage drive (hereinafter, also referred to as copy back) (for example, refer to Patent Documents 1, 2, and 3).
Also another technology has been developed which assigns priorities to the respective volumes created and allocated in the storage apparatus, and transmits copies of the data stored in the volumes to a storage apparatus installed at a remote site for disaster recovery or the like, in such order that the volumes with higher priorities can be transmitted prior to the remaining volumes (for example, refer to Patent Documents 4 and 5).